In earlier studies we have shown that dimethylcarbamyl chloride ((CH3)2NCOCl; DMCC) is carcinogenic to mouse skin and by subcutaneous injection in mice. Subsequently it was shown in this Institute (Drs. Kuschner and Laskin) that DMCC by inhalation exposure to rats caused a high incidence of squamous cell cancers of the nasal epithelium and a low incidence of squamous cell cancer of the lung. DMCC is a direct-acting acylating carcinogen and is therefore unique by comparison to other direct-acting carcinogens such as epoxides and lactones. The purpose of this work is to explore its mode of action and to extend carcinogenicity and mode of action studies to compounds related to DMCC. DMCC and the other compounds are all intermediates used in chemical industry. The other compounds to be included in the proposed work are: dimethylsulfamoyl chloride, diethylcarbamyl chloride, 1-piperidinecarbonyl chloride, ethyl chloroformate and dichloroacetyl chloride.